With the recent advance of information communication and the distribution of multimedia technologies, much discussion has been made about the base station technologies which install the base stations in the homes or offices and connect the base stations to a mobile communication network in a form of a convergence with an existing network, while guaranteeing mobility and high-capacity transmission. Also, regarding the base stations, there is a need for a new mobile communication service technology which provides the expansion of a mobile communication service area, the improvement in performance of a user service, and the increase in capacity of a base station and also supports a variety of cheap mobile communication services for users.
With such a trend, a Fixed Mobile Convergence (FMC) service and a Fixed Mobile Substitution (FMS) service started in earnest. The FMC service provides a service which can make a call with single user equipment (UE) outdoors through a connection to a mobile communication network and indoors through a public switched telephone network or IP network. The FMS service provides a service which uses a mobile communication network but can partially substitute for a wired service by making a charge for a mobile communication cheaper than that for a wired communication at a specific place, e.g., in the house. To this end, it is necessary to study technologies which increase the capacity of the base stations and optimize the cell coverage by minimizing interference between neighboring base stations within themselves or through the automatic cooperation of the neighboring base stations when new base station cells are installed.
In particular, an ultra-small base station, i.e., a femtocell, has attracted attention as an approach which can actively cope with a user's demand under an environment where a cell radius is extremely minimized up to a room space inside the home or office, reduce the service provider's capital expenditure (CAPEX) and operational expenditure (OPEX) by saving the time necessary to install an additional cell and the operational costs, and provide a radio environment, considering an equipment manufacture's new market creation and improvement in the quality of user services. The demand for femtocell standardization was proposed as a standardization item in the 3rd Generation Partnership Project (3GPP) in the early 2007, and femtocell standardization activities have been carried out as the main issue in the 3GPP2 since June 2007. The femtocell is referred to as a Home Node B (HNB) in the 3GPP, and the discussion is actively in progress about the standardizations of 3G HNB based on WCDMA and Long Term Evolution (LTE) Home evolved Node B (HeNB) based on LTE under TSG-RAN WG4.
Also, in the 3GPP2, methods for minimizing the influence of the existing networks and the interfaces between macrocells have become a main issue. While various problems such as a network architecture for CS/PS service, an interface management, a handover scheme, an access system selection, a synchronization, etc., have been under discussion, the 3GPP2 having first carried out the standardization activities took the leading position in the femtocell standardization over the 3GPP.
The femtocell technology can give several meanings to users and service providers. The service providers can provide a high-capacity service, which has been provided in an existing wired broadband service, at a low cost under radio environments by configuring cells in a small size and remarkably increasing a frequency reuse rate, and the users can receive a high-speed data service, regardless of places. Hence, such a femtocell technology provided the foundation for introduction of new services and expansion of next generation mobile communication markets following 3G.
In addition, the standardization of a Self Organizing Network (SON) technology has just been discussed. According to the SON technology, a base station configuration is automatically set when a new base station is installed, and operation information is automatically optimized by exchanging data related to a radio environment between neighboring base stations and UEs during operations, whereby the capacity of the base stations can be increased and the coverage can be expanded. The standardization of the SON technology was chosen as a study item in the 3GPP and is in progress. The extensive discussion was actively made in 2009 and it is expected that practical markets will be established after 2012.
In the SON technology of LTE-Advanced femtocells, there are a base station self-configuration technology and a base station self-optimization technology. The base station self-configuration technology generates installation parameters within itself according to the internal structure of the base station when the base station 120 is additionally installed, and performs the initial automatic installation of the base station, the identification of neighboring base stations before an operation step, relationship setup/registration, and a connection setup with respect to a core network. The base station self-optimization technology controls the base station signal intensity and optimizes the handover parameters by using signals between the neighboring base stations and traffic type information. In addition to such technologies, the LTE-Advanced femtocells apply mobility technology, a femtocell base station selection technology using a Closed Subscriber Group (CSG), and an inter-cell interference avoidance technology.
In this regard, a dynamic TNL connection setup technology of the femtocells is also treated as an important technology.
Conventionally, a base station establishes an S1 TNL connection with a Mobility Management Entity (MME) by using an initial remote IP endpoint manually inputted, and acquires TNL addresses of neighboring base stations through the MME. In this manner, an X2 TNL connection setup with the neighboring nodes is achieved. This method increases a signaling load of a network. Such a signaling load is a more serious problem in an environment where an uncoordinated, random and dense installation is frequently repeated. The signaling load may occur in macrocell base stations as well as the femtocell base stations. In the case of femtocell base stations, the signaling load is more fatal because installation/removal and power on/off are randomly conducted.